The present invention relates to electronic control apparatus for microsurgical instruments and in particular to an electronic control system that is adapted for use in intraocular surgery to control in accordance with commands received from a surgeon's foot control unit the various aspiration functions normally performed manually by a surgical assistant.
A competent eye surgical assistant provides the manual functions of: (1) aspiration, (2) reverse injection of "backflush," (3) proprioceptive feedback determination of aspiration resistance, and (4) balancing aspiration volume with infusion volume. Ideally an automated system should provide equal control and information to the surgeon. In addition, it should not be necessary for the surgeon to take his eyes from the operating microscope in order to turn and look at console dials. Moreover, console technical assistance requirements should be minimal and not vital to the surgical outcome of a procedure.
The present invention satisfies all of these criteria by providing an electronic control system that is entirely subservient to a multi-position foot control switch operated by the surgeon. The control system utilizes the safety of gravity flow infusion pressure determined by bottle height above the patient's eye. A basic low infusion pressure bottle is used in conjunction with a high infusion pressure bottle and an intermediate infusion pressure bottle is used for backflow or "backflushing" of the aspiration tubing. A peristaltic suction pump supplies aspiration and is calibrated for a low and a high suction rate that does not exceed the infusion volume capabilities of the system.
Infusion pressure and aspiration rate are controlled by the surgeon in accordance with the position of the foot control unit. The low infusion pressure bottle is always opened and provides a minimum amount of infusion pressure. The high infusion bottle is activated in conjunction with the low suction rate by initial depression of the foot switch by the surgeon. Rotation of the foot switch to the left in conjunction with the above initial switch depression initiates the high suction rate for more rapid aspiration. Rotation of the foot switch to the right stops the suction pump and limits the vacuum force to the amount in existence within the system, so as to permit the surgeon to sustain a minimal tissue impaction in the cutting aperture prior to activation of the cutter by further foot depression. Further depression of the toe switch in all three swivel positions activates cutting. Release of foot switch depression at any time immediately cancels all suction forces within the system without lowering intraocular pressure.
Control over the infusion pressure and aspiration rate provides the surgeon with several important functional capabilities. As noted, the system provides the surgeon with the ability to sustain a minimal amount of suction for tissue impaction and cutting only of the desired tissue without subsequent inadvertent tissue aspiration. In addition, pulsing of the suction pump by intermittent swiveling of the foot while maintaining initial toe depression permits the surgeon to test the aspirate and determine what tissue is being impacted or aspirated into the cutting aperture prior to cutting. Most importantly, the surgeon is provided with the capability of controlling the rate and volume of both aspiration and infusion which permits the surgeon to maintain a pressurized ocular globe throughout the surgical procedure. Moreover, as previously noted, the heights of the infusion bottles above the patient's eye, which determine the intraocular pressure in the absence of aspiration, and the calibration of the peristaltic suction pump, are selected to permit easy maintenance of the proper pressure within the eyeball.
Reverse injection of "backflush" ability to reflux unwanted aspirate from the cutting aperture is accomplished by heel depression of the rear foot switch. Further switch depression of the rear foot switch combines reverse injection with cutting.
In the common prior art practice, the information derived proprioceptively by the surgical assistant through manual aspiration, was communicated to the surgeon verbally. In accordance with the present invention the same information is provided to the surgeon by an audible sound beep of varying rapidity. Specifically, the slower rate of flow of aspirate the less frequent the sound beeps, and the faster the flow rate the more frequent the sound beeps. The audible flow device basically comprises a drip counter that is attached to the discharge side of the peristaltic pump. A photocell and a light transmitter are positioned on opposite sides of a drip tube so that drops of fluid or tissue containing fluid which fall through the transparent drip tube interrupt the light beam from the transmitter to the photo-detector. Each time this occurs, the photoelectric system triggers a "beep" tone. The faster the drops fall, the faster the beeps occur, thus providing the surgeon with a quantitative indication of the number of drops of fluid being drawn from the eye. If there is no fluid flow, no beep sound is generated.
In order to inform the surgeon when there is resistance to aspiration, the present control system is adapted to generate a different audible sound when a negative or vacuum pressure exists in the aspiration line. The sound produced is continuous and of increasing pitch as the vacuum pressure in the aspiration line increases. If the surgeon has even average tone-pitch recognition, he can readily determine the approximate suction pressure without removing his eyes from the operating microscope to view a meter. The continuous audible signal is generated by a transducer that is hydraulically connected to the system and mechanically coupled to an electrical transducer located inside the console. The output of the electrical transducer is fed through appropriate circuitry to provide a meter indication of the suction pressure as well as activating a tone signal generator which provides the audible signal.
Thus, the interplay of the two distinctive sounds and their frequencies generated by the present control system imparts first hand knowledge to the surgeon as to the actual activity within the aspiration lines, and not merely information that the suction pump is running. As is well known to those skilled in the art, a running pump does not necessarily mean that fluid flow is resulting. Rather, a running pump may be resulting in vacuum build-up unbeknown to the surgeon until a preselected maximum suction limit is achieved automatically deactivating the pump. As noted previously, it is important for the surgeon to have knowledge of initial vacuum build-up in order to ascertain that tissue impaction is being achieved. In the absence of vacuum build-up, the present control system will generate a repeating beep sound indicating to the surgeon the passage of fluid into the collection bottle.
Importantly, it will be seen that, because of the possibility of backflow in a system of the present type, the pressure transducer utilized in the present invention, along with the total harness and tubing system, can be readily sterilized. When the system is prepared for surgery, the sterilized transducer is easily inserted into a receptacle located on the front panel of the console, and thereby automatically coupled mechanically to the electrical transducer located inside the console.
The present control system is also equipped with a halogen light source to provide light to a fiberoptic cord that emits light at the distal end of the cutter probe tip when inserted into the eye. Novel means are provided for rapidly switching lamps in the event of a lamp burnout. In particular, if a lamp burnout should occur during surgery, a new lamp is rotated into position by pulling out a knob located on the front panel of the control unit. When the knob is pulled outwardly, a carousel inside of the unit rotates a spare lamp into proper alignment with the end of the fiberoptic cord and electrical power is automatically switched from the main lamp to the spare lamp by means of a switch that is actuated by the rotation of a cam connected to the axle of the carousel.
Further objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :